2.5 inch exhaust is too big for an N/A b16. If he gets cams with more lift and duration he's going to need new springs and retainers at the least, I suggest new valves as well. An intake mani is not going to do any good on a stock internal b16.what kind of tb was it. do a 2.5 exhaust get bigger cams, cai, get a intake manifold. then turbo